1. Field of the Invention
The present invention relates to a resilient prosthetic foot that has a reinforcement member to provide reinforcement. More particularly, the present invention relates to a prosthetic foot having at least a resilient forefoot member, and at least one resilient reinforcement member that is engaged after the forefoot or heel members move from a normal range of movement to an extreme range.
2. Prior Art
Many individuals have lost a limb for various reasons including war, accident, or disease.
In most instances these individuals are not only able to live relatively normal lives, but physically active lives as well. Often times, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb.
With respect to prosthetic feet, the development of a functional and natural artificial foot has been limited only by material and imagination. Many designs have attempted to copy the anatomy of the foot or simulate its actions by replacing the bones and muscle with various mechanical components. Other designs have departed radically from mere anatomical copying or mechanical simulation by replacing the entire foot with an energy storage element, such as a spring. As the user steps onto the foot, the user's weight compresses the spring. As the user moves forward, the user's weight comes off the foot and the energy stored in the spring is used to propel the user forward.
Examples of such energy storing, spring-like feet having a forefoot member and a heel member include U.S. Pat. Nos. 5,037,444 and 4,547,913. U.S. Pat. No. 5,037,444 issued Aug. 6, 1991 to Phillips discloses a prosthetic foot having a forefoot portion and a heel portion. The forefoot portion has an attachment section, a curvilinear spring section, an arch section, and a toe section formed integrally with one another. The heel portion is removably attached to the forefoot portion at the intersection of the arch and toe sections by a bolt and nut. An elastomeric wedge is inserted between the forefoot portion and the heel portion. U.S. Pat. No 4,547,913 issued Oct. 22, 1985 to Phillips discloses a prosthetic foot having a forefoot portion and a heel portion. The forefoot portion and the heel portion are bound together with a "resin impregnated filament binding" by winding the filament around the members.
The stiffness of prosthetic feet typically vary according to the intended use. Feet intended for everyday use typically require a soft feel, and thus incorporate a loose spring. Feet intended for athletic use typically require strength, and thus incorporate a stiff spring. Although different prosthetic feet may be changed to suit the particular activity, such switching is inconvenient and at times it is impossible, such as a sudden need to run to catch, or avoid being hit by a bus. Feet designed for particular purposes are typically unsuited for other purposes. Stiff, athletic feet are too hard for everyday use, and loose, everyday feet are too fragile for athletic use. Multiple-use feet have been designed which are capable of many different uses, but without being particularly well suited for any use.
In addition, the performance of these energy storing feet has been altered in various ways, such as by using multiple springs in various configurations, using bladders or resilient materials disposed between various elements, and using multiple springs that deflect at different intervals of foot deflection to add resistance.
U.S. Pat. No. 5,290,319 issued Mar. 1, 1994 to Phillips discloses a prosthetic foot having a forefoot portion, a heel portion, and an auxiliary member disposed above the forefoot portion. A bladder is disposed between the auxiliary member and the forefoot portion. The pressure in the bladder is varied to adjust the performance of the foot. In this configuration, the auxiliary member is a structural member against which the bladder is compressed.
U.S. Pat. No. 5,387,246 issued Feb. 7, 1995 to Phillips discloses a prosthetic foot having a forefoot portion, a sole member, and an auxiliary or secondary stiffness member disposed above the forefoot portion. The secondary member adds stiffness to the foot when the foot is deflected sufficiently forward such as to engage the secondary member.
U.S. Pat. No. 4,721,510 issued Jan. 26, 1988 to Cooper et al. discloses a prosthetic foot having a relatively flexible primary foot member and a relatively stiff secondary foot member disposed above the primary foot member such that the spring force of the foot is increased as the primary foot member deflects to the secondary foot member.
It is desirable to further improve prosthetic feet to better simulate real feet, and improve the performance and response characteristics of prosthetic feet. Therefore, it would be advantageous to develop a prosthetic foot capable of more naturally simulating a real foot. It would also be advantageous to develop a prosthetic foot having a reinforcement member. In addition, it would be advantageous to develop a prosthetic foot having various degrees of stiffness.